To me, detonation sounds like a bunch of rattle can paint cans being shaken incredibly fast. It usually happens when you lug the vehicle, like going uphill and just barely giving it some gas. When you let off it stops. A friend of mine's Dad was an old timey mechanic, and he would set timing by ear that way. Run it up till it rattles a little, then ease it back down a little at a time till it quit rattling. He used to roll his eyes at us "Boys" and our timing light....lol.
